It's not actually a 650Watt but a 550Watt that has a lower combined 3.3v + 5v wattage than some good 400 watt PSU's.
The Enermax 651 has no pot adjustment but the 5v rail can be increased by the insertion of a 1K ohm pot in line with R82 on the PCB. I didn't have a 1k ohm pot so just used an 820 ohm resistor instead.
here are my voltages now with a EG651P-VE.
I also had a 400 Watt Antec recently but I never even plugged it in. I opend it up and it was such a mess inside with little extra PCB's and add on wires it was no good for my use.
The Enermax is working fine and just to ensure this topic stays in the water cooling forum here's a pic of mine water cooled